I don't know yet if there is a season six, but it's not going to go on forever

Downton Abbey creator Julian Fellowes

Downton Abbey last appeared on British TV during a Christmas Day special which showed the Crawley family visiting London.

Fans are currently waiting for the fifth series to Downton to be broadcast later this year.

Lord Fellowes added: "It's for NBC Universal and it will happen when Downton finishes because I just couldn't do both at once.

"I haven't written it yet, but it's about the old aristocracy, the Winthrops and the Stuyvesants and the new money of oil and gas and shipping in the 1870s. It will all be fiction - it won't be real people - but when those families descended on New York, they took over."

Michelle Dockery stars as Lady Mary Crawley on Downton Abbey [AP]

The 64-year-old also said that if the Crawley family existed they would still be running the Downton Abbey estate today but is a "businesslike" manner.

He said: "My own belief is that they would survive, but they would be living in a back wing - and you could buy a ticket to visit and they would only come out in the winter."